Mounting for electrical devices and method of securing same in porcelain insulators



March 9,1954

Filed June 2, 1950 SHIT/1577c ADHESIVE M! TUE/IL RUBBER HND FHENOL/CHES/IV G. F. M MAHON MOUNTING FOR ELECTRICAL DEVICES AND METHOD OFSECURING SAME IN PORCELAIN INSULATORS 2 Sheets-Sheet l IN VEN TOR. fieoyefflc/lfaa March 9, 1954 F. M MAHON 2,671,822

MOUNTING FOR ELECTRICAL DEVICES AND METHOD OF SECURING SAME IN PORCELAININSULATORS Filed June 2, 1950 2 Sheets-Sheet 2 IN VEN TOR.

over a wide range of operating temperatures. "attempting to achievethese features,

tends to grow with age.

Patented Mar. 9, 1954 UNITED STATES PATENT OFFICE.

MOUNTING "FOR ELECTRICAL DEVICES AND METHOD OF SECURING SAME 'IN PORCE-LAIN INSULATORS poration of Delaware Application J une 2, 1950, SerialNo. 165,758

This invention relates, generally, to mounting means for electricaldevices and has particular relation to the construction thereof andmethods of making the same.

Electrical devices, such as :fuses, foruse on electrical distributionsystems operating at volta es ranging upwardly from 2360voltsutilize-porcelain dnsulators; Thcyserve .a :dual function.Provisionis made for mounting the terminals of the "device in insulatedspaced relation in such. menner as to withstand line to ground voltageand line to line voltage after operation of the device and opening ofthe'circuit. In addition the insulatorzis supported, usually from across arm, and

the support is arranged withrespect to thetermi- *nals to provide thenecessary creepage distance place in the cavities by cement. Theterminals may be and usually are separately mounted on inserts while thesupportcomprises an insert one end of which is cemented in a cavity andthe otherend is arranged for clamping to a cross-arm or the like.Alternatively an insert may be provided to which a support "bracket isclamped.

In order to be satisfactory from a mechanical and electrical standpoint,the inserts must be secured in the cavities in such manner that the"joints between the cement and the inserts on the one hand and betweenthe cement and the cavities on the other are tight and strong, weatherresisting, non-corrosive and temperature resistant In ttneatll Portlandcement has been employed. This cement contains no sand and is mixed withdefinite amounts of water. Usually the cement is placed in the cavitiesand the inserts are embedded therein, the inserts being held by jigs inorder to provide proper alignment. The assembly then is placed in asteam room or humid chamber at temperatures in the neighborhood of 100F. for twenty-four hours or longer until the cement is set. Then thejigs are removed and the assembly remains in the steam room for a'time,such. as

'four to fiive days, in order to insure proper hydration. Thereafter theporcelain with the cemented inserts therein is removed from the steamchamber, the excess cement is cleaned off of the insulator and it isprepared for final assembly with the finished product.

Experience has shown that Portland cement It expands or increases involume dueto combination with water and carbon dioxide 'from' theatmosphere.- In

3 Claims, (Cl. 174-9169) some instances after several years ofoutdoor-exposure, the growth is enough to cause failure or crackingofthe porcelain. Thistakes place more often in localities near theseaboard than it does in areas away from a salty atmosphere. There are.other causes of failure also. One is'the result of rusting of the insertafter the galvanized or zinc coating thereon has failed. Attempts havebeen made to overcome these conditions by coating the portions of theinserts to be located within the cavities with. a thin resilient paint.Usually asphalt or wax is used. The sanded surface of the cavity in theporcelain also is given a-thin coating of such compound. Such a coatingon the insert tends to arrest chemical reaction of the alkaline cement.When such reaction-does take place, excessive looseness of the insertoften results when stresses are applied thereto under operatingconditions. Looseness also may result from. the use of too thicka layerof wax or paint.

Another and serious objection to the use of Portland cement is the timerequired for the cement to set. On a mass production basis it isnecessary to usea large number of jigs or holding fixtures. A relativelylarge space for the steam room is required tohandle any quantity ofporcelain-to which insulators are being cemented.

In addition to the use of Portland cement for securing metallic insertsin cavities in porcelain insulators, other materials have been proposed.These include molten metallic alloys and sulphur and silica cement. .Themost successful alloys which have been used contain lead. antimony, tinand cadmium in varying amounts. Such alloys ar expensive. There is atendency toward loosemess of the inserts under load stresses andvibration. This is caused by the cold flowing of the alloy under stresswith a result that it no longer is in close contact with the surface ofthe insert. The sulphur and silica cements act pe- 'culiarly in takingon certain crystallization changes with time and temperature. Poorstrength and growth with age 'sometimes'occur. A particularly desirablesulphur sand cement is one containing sulphur, sand '(silica) andan'olefine polysulphide. The oleiine polysulphides conlstitute a classof synthetic rubber because of their similarity in characteristics torubber. such cements are employed, a construction much When moreresilient than that provided by Portland c- .ment is obtained. This isan important characteristic particularly when it is considered that anis resiliently mounted therein, such action may not take place.

There is, however, a, very serious difllculty encountered in the use ofcements containing sulphur, silica, and olefine polysulphide. They havevery poor adhesion to the insert whether made of bronze or galvanizediron or steel. Although the joint with the insert at first appears to betight when the cement has solidified, under continual loading andvibration the inserts become loose. Despite this the cement itselfremains dense and strong.

Accordingly, the principal object of this invention is to provide forsecuring metallic inserts in a porcelain insulator in such manner thatthe foregoing objections will be overcome. Other objects of thisinvention are: To provide, a, good and intimate bond between the cementand the metallic insert; to maintain and utilize the resilientcharacteristics of sulphur cement in the securing of metallic inserts inthe cavities in porcelain insulators; and to secure the inserts incavities in porcelain insulators in such manner that substantially nochange takes place over the years in the characteristics of the cementinsofar as its eilects may be on the secure holding of the inserts inposition.

Other objects of this invention will, in part, be obvious and in partappear hereinafter;

For a more complete understanding of the nature and scope of thisinvention, reference may be had to the following detailed description,taken together with the accompanying drawings,

in which:

Figure 1 is a sectional view, at an enlarged scale, illustrating how ametallic insert can be secured in a cavity in a porcelain insulator inaccordance with this invention;

Figure 2 is a longitudinal sectional view of a generally cylindricalinsulator in which inserts are provided in the ends for mounting anelectrical device, such as a fuse or disconnecting switch, and acentrally located insert is provided for mounting the insulator on across arm;

Figure 3 is a view, similar to Figure 2, showing the inserts in spacedrelation to the cavities into which they are positioned for cementing;

Figure 4 is a view, partly in side elevation and partly in section,showing a porcelain housing in which a fuse device is mounted on insertswhich are assembled in the housing in accordance with this invention;

Figure 5 is a longitudinal sectional view of the housing shown in Figure4 with the inserts in place; and

Figure 6 is a view similar to Figure 5, at an enlarged scale, showingthe inserts in spaced rela tion with respect to their cavities in therear wall of the housing.

Referring now particularly to Figure l of the drawings where a typicalassembly of an insert in a porcelain insulator is disclosed, thereference character I!) designates the porcelain insulator which may beof the conventional wet process type. The insulator l0 duringmanufacture is provided with a cavity H having a sanded surface l2. Thecavity II is arranged to receive a metallic insert l3 which may be ofbronze or galvanized iron or steel. The insert I3 is secured in positionby means of cement II. Preferably the cement I4 is a sulphur silicacement containing olefine polysulphide. The silica content may rangefrom thirty-five to forty per cent, the sulphur content may range fromsixty to sixty-five per cent, and the oleflne range from one to five percent. Specifically, percentages of the order of thirty-fivesixty-fourone, respectively, have been used. Also, percentages of the order ofthirty-five-sixtyflve, respectively, have been used.

Prior to placing the insert l3 in the cavity I I, it is coated with athin layer l5 of a synthetic adhesive. This is accomplished by dippingthat portion of the insert l3 which is to be located within the cavityII in a synthetic adhesive containing rubber and phenolic resin.Preferably the synthetic adhesive contains a fusible phenolformaldehyderesin and synthetic rubber made by polymerizing 1,3-butadiene andacrylonitrile in aqueous dispersion. For illustrative purposes the layerI! of synthetic adhesive has been shown several times thicker than itactually is. In etfect it is a very thin coating and is formed, asindicated, merely by dipping the insert I3 into a synthetic adhesive ofthe character described. In cementing the insert IS in position in thecavity I I, after it is dipped in the synthetic adhesive l5. it isplaced in the cavity I I and held therein by a suitable jig. Then thecement H, at a temperature of from 290 F. to 300 F., is poured in thespace around the insert IS. The cement l4 cools quickly and, in sodoing, it adheres to the sanded surface l2 of the insulator l0 andreacts with the rubber in the synthetic adhesive 15 containing the samewith a vulcanizing action to provide a satisfactory bond with the insertI3. The synthetic adhesive 1-5 adheres to the cement I 4 on the one handand to the insert IS on the other.

It prevents any chemical reaction taking place between the sulphur inthe cement I4 and the zinc or galvanizing coating on the insert l 3 whenit is employed. The synthetic adhesive I"! provides a resilientimpervious layer between the insert l3 and the cement ll. Also itprovides thermal insulation therebetween which permits the cement I4 toset more uniformly throughout.

When a metallic insert I3 is secured in the cavity l I of a porcelaininsulator ID in the manner described, the insert is highly resistant totorsion and cantilever loading. The cement l4 does not appear to besubject to growth. One reason for this is considered to be the absenceof iron therein. Since there is a very tight fit between the cement l4and the insert l3 and since this relationship is maintained, there is nolikelihood of the insert I3 becoming loose even though it may besubjected to severe mechanical shock resulting from the blowing of afuse or the stopping of a switch blade in a ninety degree or 180 degreeposition by a'stop.

While the synthetic adhesive 15 has been described as containingsynthetic rubber, it also may contain natural rubber.

Illustrative applications of the assembly of an insert in a porcelaininsulator as shown in Figure l and described above now will be setforth.

In Figure 2 of the drawings there is illustrated, generally, at IS auniversal single insulator mounting of the character disclosed in Bakerap-- plication Serial No. 16,268, filed March 22, 1948, and assigned tothe assignee of this application now Patent No. 2,606,954. This mountingincludes a porcelain insulator l9 that is generally cylindrical incharacter and has cavities 20 at the ends arranged to receive inserts2|. V The inserts 2| may be galvanized steel rods bent to the shapesindicated with flattened terminal receiving ends 22. The inserts 2| havecorrugated ends 23 to facilitate holding the same in position in thecavities 29 which have sanded surfaces 24. The inserts 2| are held inposition in the cavities 29 by cement 25 which, as describedhereinbefore, comprises sulphur, silica, and olefine polysulphide in theamounts set forth. Prior to insertion in the cavities 29 the corrugatedends 23 are dipped in a synthetic adhesive, containing synthetic ornatural rubber and phenolic resin as described, so as to provide a thinlayer 26 thereon.

The porcelain insulator l9 also is provided with an intermediate cavity29 for receiving a support insert 39. It has a support flange 3| formounting on a suitable cross arm or the like. At its other end theinsert 39 has a corrugated end 32 for positioning within the cavity 29which has a sanded surface 33. A cement 34, identical with the cement25, serves to hold the insert 39 in position. Prior to placing theinsert in the cavity 29, it is dipped in a synthetic adhesive containingsynthetic or natural rubber and phenolic resin to provide a layer 35 ofthe same thereon.

In Figure 3 of the drawings the manner in which the inserts 2! and 39are assembled with the insulator i9 is illustrated. The inserts 2| and39 with the layers 26 and 35 of synthetic adhesive thereon are held inposition in the respective cavities 29 and 33 by suitable jigs. Thecement 25 and 34 is poured into the cavities 29 and 33 which aresuccessively positioned in the upright position for receiving the same.

The present invention can be employed for securing inserts for thedropout fuse that is illustrated, generally, at 49 in Figure 4. Thedetails of the construction of the dropout fuse 49 are set forth moreclearly in Ramsey et al. United States Patent No. 2,292,341, issuedAugust 4, 1942, and, accordingly, will not be set forth herein. Thedropout fuse 40 comprises a porcelain housing or box, shown generally at4 l, which is closed on the rear, top and sides and is open at the frontand bottom. The housing 4! carries a door 42 on which a fuse tube 43 isslidably mounted. The fuse tube 43 is slidably mounted in a sleeve 44that is carried by the door 42. In turn the sleeve 44 is rockablymounted on a hinge bracket 45. The fuse tube 43 is provided withcontacts 46 and 47 that are arranged to cooperate with stationarycontacts 48. As shown more clearly in Figure 5,

the hinge bracket 45 is arranged to be carried by an insert 49 while thecontacts 48 are arranged to be carried by inserts 50 and 5|.

The inserts 49, 50, and 5| are located, respectively, in cavities 52,53, and 54 having sanded surfaces and located in the front side of therear wall of the housing 4|. These inserts are held in place by cement55, 56, and 51, respectively, which, as previously described, containssulphur, silica and olefine polysulphide. Prior to placing the inserts49, 50, and 5| in their respective cavities they are dipped in asynthetic adhesive containing synthetic or natural rubber and phenolicresin so as to provide layers 58, 59, and 60, respectively, thereon.

The porcelain housing 41 is supported on the rear side by a supportbracket 6i which may be secured by a bolt 62 to an insert 63. It will benoted that the insert 63 is located in a cavity 64 having a sandedsurface and opens rearwardly from the back wall of the porcelain housing4|. The insert 53 is secured in position by cement 65 which comprisessulphur, silica, and olefine polysulphide. Prior to placing the insert63 in the cavity 64, it is given a. coating 66 of synthetic adhesivecontaining synthetic or natural rubber and phenolic resin.

In Figure 6 there is illustrated the manner in which the inserts 49, 5D,and 63 are assembled in their respective cavities. As indicated, theyare first dipped in the synthetic adhesive to provide relatively thinlayers of the same thereon. Next they are held in their respectivecavities by a suitable jig. The cement then is poured in the cavitiesand is allowed to set.

Since certain further changes can be made in the foregoing constructionand method and different embodiments of the invention can be madewithout departing from the spirit and scope thereof, it is intended thatall matter shown in the accompanying drawings and described hereinbeforeshall be interpreted as illustrative and not in a limiting sense.

What is claimed as new is:

1. Method of securing a metallic insert in a porcelain cavity whichcomprises: coating the entire surface of that portion of the insert tobe placed in the cavity with a film of synthetic adhesive containingrubber and phenolic resin, 10- eating the coated portion of the insertin position in the cavity, filling the remaining space in the cavitywith molten sulphur cement carrying in solution an olefine polysulphideat a temperature ranging from 290 F. to 300 F., and allowing the assemblto cool to room temperature.

2. Mounting means for electrical devices and the like comprising, aporcelain insulator having a cavity therein provided with a sandedsurface, a device supporting metallic insert in said cavity, a syntheticadhesive coating containing rubber and phenolic resin on the portion ofsaid insert within said cavity, and a filling of sulphur cement carryingin solution an olefine polysulphide in said cavity, said fillingadhering to said sanded surface and to said adhesive coating andresiliently mounting said insert without looseness.

3. Mounting means for electrical devices and the like comprising, aporcelain insulator having spaced terminal insert receiving cavities anda support insert receiving cavity therebetween, said cavities havingsanded surfaces, terminal inserts in said terminal insert receivingcavities and a support insert in said support insert receiving cavity, asynthetic adhesive coating containing rubber and phenolic resin on thatportion of said inserts within their respective cavities, and a fillingof sulphur cement carrying in solution an olefine polysulphide in eachof said cavities, said filling in each cavity adhering to the sandedsurface thereof and to the adhesive coating of the insert therein andresiliently mounting the same without looseness.

GEORGE F. MCMAHON.

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